Developing the DIY "Champ" for first time builders

[RJ Guitars]

RJ,
After fiddling with mine and playing it awhile, I have found that with a 12ax7 preamp tube and a 6v6 power tube, the sound is nice and clear turned down low, but gets honky and a bit muddy turned up, and the overdriven sound is unpleasant to me. As a result, I haven't bee playing it much at all, since clean tone playing at low levels isn't my bag at the moment. I might try a 5751 input tube, or a 12at7 and see how that sounds, then play around a bit with putting in a simple tone circuit. It may be, as you seem to be suggesting, that voltages are the main contributor to the tone of this amp.
Cheers,
Greg

Greg, we should tweak on that amp and bring it into a form that will make it fun for you. As a platform for learning this has been a great project but it's also a fact that the Champ amp has a place in most players arsenal where it's very useful. Watch as we tweak on my build and let's see if we can find whatever is needed to bring some magic to your amp. Feel free to jump in and use this thread to sort things out. One reason I did this in a public forum is that it provides you with the best tech support network on the planet for guitar tube amp info. You'll get some great help from these guys and we'll all be a bit wiser when we get to that happy place.

rj

[gktamps]

That sounds great, RJ. I just picked up a Jeff Beck Strat today and want to give it a try through the amp. Could be the front end is getting hit pretty hard by my humbucker guitars, which could give me a clue about how the preamp stage is set up (gain, headroom).
I'll let you know how that goes tomorrow.
Thanks!
Greg

[RJ Guitars]

Greg,

that is going to be a fun guitar.

I did fall victim to some of my old habits and reduced the plate resistor values on the preamp tube just to hear the difference. I read up in Merlin a little before hand and what I understood was that the lower value would be more common in an amp you wanted for clean tones. He suggest 47K so of course I went with 39K and and 33K to make sure I went far enough... and I liked what I heard. Picked up a little clean headroom but still didn't like the overdriven tone so much. I went back to the 6SL7 tube and it sounded a little bit better and had about the same headroom as the 6SN7. Improved but nothing amazing yet.

I also tried a half dozen different output tubes just to hear them. A few Russian choices - 6N6C and 6N3C, plus some NOS 6k6GT, 6W6GT, and a 6Y6GT. All of them sounded great and had a nice glassy clean tone but still nothing fantastic when overdriven very hard.

On this latest iteration with the very low voltage Power Tranny I have padded the preamp output more than in the stock Eagle 100, but maybe not enough yet. It seems to be a narrow window where the overdrive goes from useful to buzztone.

More changes and measurements to come. I really want to understand how to find the cathode resistor sweet spot and make sure I have that right. That will be where I focus next.

rj

[surfsup]

RJ I just sent you a big 'ol email on some thoughts but you know what? I'm going to get off my arse and put in an octal preamp tube on the supre and check it out...why the heck not...I assume a few extra mA of current will unaffect the PT rating.

[jeremyb]

RJ, is there a 240V input option on your kits? Great work btw, kits look fantastic!

[RJ Guitars]

Jeremy,

I have a couple different transformer options that allow for 240 operation. Let me look at exactly what I have and if you send me an email I'll reply back with details.

thanks,

rj

info at rjguitars dot net

[Whodatpat]

Do you have what would amount to the current build recomendations and schematic for this amp? I am seeing lots of great trial and error based on the original. But I would like to avoid some of that to stay closer to that less than $100 number.

Patrick

[surfsup]

Whodatpat, i doubt you'll be under $100 if you source it yourself. Rj was kind enough to do the heavy lifting AND pass on the wholesale (most) to those who got a kit from him. Shipping alone will kill ya.

Update, i have removed the fx loop passives and jacks and still have the second tube. I also fixed the weirdness and narrowed it down to the cause though my solution was to remove it. I had the tone stack on a switch between a 22k and a 1k5 and when switching from thw 22 to the 1k5 And back agaon to the 22k, the amp would oscilate at full volume. Leaving it off for a long time fixes it. So i removed the switch and wired in a dedicated 33k, but anyone have an idea as to why this happens? The amp was fine with either as long as i wasnt switching.

My next plan is to have input to gain to cf to ts to gain to cf to pa to see how that sounds. I wanna see if i can get some 2nd harmonic compression out of each cf with low Rks

Then i might try an octal V1 like RJ is doing now except a 6sn7. You can see the 5Y3 glowing in this shot, I believe from the description someone provided earlier its an "original" so I am also thinking of swapping the PT/OT and drilling another hole and going PP with the 5Y3 recto.

[img600]http://chicagocadcam.com/ChrisHahn/supre/Supre5Y3.jpg[/img][/img]

[gary sanders]

Heres my 2 cents on a SE build I just did:

PT,Ebay-$19
OPT, (Hammond!)Ebay-$26
Chassis,ACK-$10
Cab-Old Silvertone 1451
Speaker-Jensen 8" from Conn Leslie
Components and board-From the bin....($10-15)
Tubes-Stolen JUST KIDDING!!!! GE 5Y3 ebay $8,GE 12AX7,Amparex EL84 From the bin

Three cheers for GOOD ebay parts and >$100 tube amps!

The best that little cracker box ever sounded.The original 50C5,12au6 circuit sounded like ass!

[RJ Guitars]

That is very cool... any gut shots or schematics and maybe a couple of your trial and error findings to add to our corporate knowledge?

thanks, rj

[M Fowler]

Gary,

Nice amp and that's the way to do this project effectively to keep cost down. A guy could even build a cab like that and tolex it or spray bed liner on it or stain the wood and still have a kool retro looking good sounding amp.

Mark

[surfsup]

Have you got the 5Y3 in there just to drop the voltage?

[gary sanders]

No,its basically a champ with an EL84.I have never had an amp with a tube rec. so I just went by the schematic to see how it worked.Theres a bright switch,a tone stack bypass and the bypass cap on the EL84 can be doubled with the last switch for a low end boost ,say if youre playin a strat through it.I did do quite a few things in there different.Will draw up a schematic later.Its a really cool amp.This is the one I was having the high voltage trouble with.All good now.

I got that amp WITH the Silvertone U1 ( like this one http://www.ebay.com/itm/1959-Vintage-Si ... 2a144b8897 ) ,both for $30 at the Salvation army thrift store a few years ago.Sold the guitar for $300 and now heres the amp. ( wish I had kept the guitar,later finding that Hendrix's first was the same model)

Its a keeper for sure.Cant wait to do a small coffee house gig with it.The Jensen is SUPER sweet.I wish I had ten more of those speakers.You can get them on Ebay for 10-20 bucks.Ive been watchin them lately.I believe its called a CR8 or CS8,something like that.You can tell by the basket on the back and the wire guide on it.I think it would be cool to have a cab with two of them in it.OK Im babblin....I'll get the real info up later this evening,maybe an audio clip if i have time

[gary sanders]

That is very cool... any gut shots or schematics and maybe a couple of your trial and error findings to add to our corporate knowledge?

thanks, rj

Heres a pic I took.Had to pull it to change the cathode resistor on the EL84 from 220R to 330R.Much better and doesnt sound like its working so hard.Its a bunch of stuff crammed in a little box but hey,thats always good.And three cheers for Home Depot counter top samples!!!!!

[Ed_B]

Hey all,

New poster, long time reader,...lol

This is a question from a noob, about a year, with a little help from a friend Marlon Reed (mcrracer) who has guided me through 6 builds. I am trying to figure out why this 5 watt "eagle" sounds so good , until you turn it up past about half then it sounds weired like almost a slight delay and not enough umph and soaked in to itself , pardon my description. I did talk it over with Marlon, but with his sight as it is ,and never having built this amp he could only offer a couple of suggestions , we changed a couple values with little or no change. I am currantly using EH tubes, although I've tried quite a few. With the Allied 6k49vg b+1 is 315 b+2 is 271 b+3 is 239 Any thoughts, tips, HELP, would be appreciated I welcome all comments and will soak it all up

Thanks Ed B